U.S. Pat. No. 2,824,546 discloses that natural follicle hormones may be utilized for fattening cattle, hogs, and other domestic animals, for hormonal castration of domestic animals, especially male animals, such as boars, steers, cockerels and the like, and for various other veterinary purposes. More particularly, U.S. Pat. No. 2,824,546 teaches that natural follicle hormone preparations when administered to male animals will enhance fattening of the animal if the hormones are administered about three months before the animal is to be slaughtered.
Differentiation of the rodent brain during the neonatal period, which results in sexual dimorphism, has been extensively investigated previously. (See for example, Barraclough, C. A., Endocrinology 68, 62 (1961); Barraclough, C. A. and Gorski, R. A., Endocrinology, 68, 68 (1961); Harris, G. W. and Levine, S., J. Physiol., 163, 42 (1962); and Barraclough, C. A., Endocrinology 78, 1053 (1966).) Experiments involving castration of male, or androgenization of female, neonates have demonstrated that androgen, which is normally secreted by the male gonad during the neonatal period and probably aromatized to estrogen within neural tissues (Reddy, V.V.R., et al, Endocrinology 94, 117 (1974); Weisz, J. and Gibbs, C., Neuroendocrinology, 14, 72 (1974); and Lieberburg, T. and McEwen, B. S., Brain Res., 85, 165 (1975)) suppresses hypothalmic positive feedback control centers and thus cyclic gonadotropin secretion (Mennin, S. P. and Gorski, R. A., Endocrinology, 96, 486 (1975) and Harlan, R. E. and Gorski, R. A., Endocrinology, 101, 741 ( 1977)).
Less attention has been focused on investigation of the development of tonic gonadotropin secretion, which may be conveniently studied in the male, in whom complexities due to cyclicity are reduced. We report here a developmental event, occurring during the perinatal period, which is necessary for normal subsequent tonic gonadotropin secretion and consequent testicular maturation. The existence of this event has been demonstrated by inhibiting testicular development in male mammals by administering pharmacologically effective doses of androgen.